This invention relates to an improved system for restraining cargo during transportation. More particularly, this invention relates to a novel lashing for securing and restraining undesired movement of drums, boxes, rigid and flexible containers, palletized or not palletized, within the interior of a container for sea, air, rail or overland transport. Moreover this invention relates to a system of enhanced polyester filament strand denier content of reinforcing material with characteristics to efficiently control load shifting during transport.
Most shipments for export, both in the United States and abroad, are placed within intermodal containers. Intermodal containers are often loaded with cargo in containment isolation enclosures such as boxes, fifty five gallon closed head drums, super sacks or plastic reinforced bags, plastic wrapped bundles, cased goods, metal coils, specialty heavy paper rolls, plastic or metal containers mounted on pallets, and the like. Although each containment enclosure may be quite heavy and stationary at rest, the mass of a transport load can produce considerable momentum force as a result of ship, aircraft, railcar, or truck changes in motion such as for example by acceleration, deceleration or a change in direction.
Intermodal containers generally have standardized dimensions of twenty or forty feet in length and are fabricated with steel, corrugated sidewalls which are structurally self-supporting and very rugged. Intermodal containers are usually stacked onto ships for ocean transport and are subjected to wave forces of yaw, pitch, heave, sway, and surge. Each of these forces has the potential to impart substantial damage to contents within the intermodal container. In this, when a container changes direction or speed, unsecured cargo within the container tends to continue along an existing path until it contacts an interior wall of the container. Without some type of restraint and/or cushioning system, cargo tends to build up considerable momentum, independent of the container. The amount of momentum is equal to the mass of a load multiplied by its velocity. In the case of large cargo loads, even a small change in velocity or direction can generate substantial motion forces.
For air travel, although commercial passenger flights avoid air turbulence, in some instances clear air turbulence or even rough weather is not avoidable. Moreover for cargo transport, per se, when passengers are not involved, air carriers might use the most direct route regardless of weather conditions.
On overland routes intermodal containers are often “piggybacked” onto railroad flat cars and/or truck trailers. Rail cars may be made up and coupled together by a humping process within a switching yard. When a railroad car is rolled into a stationary string of cars, the impact causes the car couplings to lock together with a jolt. This impact can apply an impact force to cargo within the rail car. Moreover, during transport, railway cars are subject to braking forces, run-in and run-out, coupler impact over grades, rail vibration, dips in the track, and swaying. In a similar manner trucks are subject to stopping and starting forces, emergency braking, bumps and swaying from uneven road beds, centrifugal forces on curves, vibration, etc. all of which tend to shift gravity secured loads within a container.
When cargo contacts the interior walls or doors of a container, the force necessary to reduce cargo momentum to zero must be absorbed by the goods and/or the container. Such forces can result in damage to cargo, damage to interior walls or doors of the container, damage to cargo packing, and moreover may create dangerous leaks if the cargo is a hazardous material. Accordingly, it is undesirable to permit cargo to gain any momentum independent of a container during transport. This is accomplished by restraining the cargo within the container so that the cargo and the container are essentially united and operationally react as one unit during transport.
In order to secure the load during transport and minimize undesired shifting and damage, load containment enclosures are often secured to the floor and/or sides of an intermodal container, boxcar or trailer using specially fabricated wood framing, floor blocking, rubber mats, steel strapping, heavy air bags, etc. All of these previously known systems for securement have limitations associated with construction cost, lack of strength sufficient to secure dense loads, etc. Moreover, although rear doors of a truck trailer may be relied on to at least partially secure non-hazardous materials such as food-stuffs, tissue or soft paper products, furniture, appliances, etc., for hazardous materials, and many other types of loads, the rear doors of a container may not be used to even partially secure a load. In fact, in order to comply with Department of Transportation and Bureau of Explosives regulations, hazardous materials are not permitted to come in contact with or “touch” rear container doors during an impact.
In the past, cargo was often stabilized by a method of load-locking with lumber bracing. This system involves strategically placing lumber between a load face and rear doors of a container. This, however, can be a costly, time consuming, and generally inefficient means of securing a load. A lumber based bracing and blocking process requires skilled carpenters and is often outsourced to contractors. Moreover, wooden barriers can be time consuming to install.
Wood bracing can be somewhat brittle and subject to failure as a result of an abrupt impact. Further conventional methods of load-blocking with lumber bracing simply can not perform some tasks. For example, the most efficient means of filling an intermodal container is eighty, fifty-five gallon drums, double stacked within a twenty-foot long container. However, if eighty barrels are loaded there are only approximately four inches between the load face and rear doors of a conventional intermodal container. Four inches is not enough space to put sufficient lumber to brace a load of eighty drums adequately. Consequently, when wood bracing is utilized as a system of restraint, shippers are forced to ship containers that are not filled to capacity. This reduces transport efficiency and increases transportation costs. Moreover, some types of wood, such as conifer woods, are not acceptable to cross international boundaries without certification of special fumigation or heat treatment processing.
The Department of Transportation has established a standard to determine if a particular restraint system is capable of adequately securing hazardous cargo. In certain instances, conventional load-locking and lumber bracing has not been structurally rugged enough to receive approval to ship hazardous cargo.
Other known means of restraint such as ropes, metal or plastic straps or stands and the like appearing in the past have tended to be expensive, exhibit impaired performance and are often not functionally suitable to restrain desired loads.
In some instances a trailer or boxcar may be used for shipping where only a partial load is carried. A partial load might be positioned within a central location of a trailer. In this instance it may be impractical to construct wooden front and rear dunnage sufficient to secure a load where the front of the trailer is not utilized. Additionally some partial loads are not symmetrically positioned on a pallet and securement must therefore accommodate an asymmetric load situation.
Improved cargo, flexible lashing, restraint systems and methods, such as disclosed in the related patents noted in paragraph [0001] above, have offered a substantial advance in the field of securement of loads within intermodal containers and the like. A continuing need exists, however, for securing lading within intermodal containers, air transport containers, boxcars, truck trailers, and the like that is functionally effective, cost-efficient, labor-efficient, and is concomitantly able to comply with Department of Transportation and Bureau of Explosives regulations. In this, a need exists for securement systems that have enhanced polyester filament strand denier efficiency and cost characteristics while limiting undesirable cargo movement within a container.
The limitations suggested in the preceding and/or desirable characteristics for advantageous load restraint systems are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness or desirability of cargo restraining systems known in the past. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that cargo-restraining systems appearing in the past will admit to worthwhile improvement.